Telephone system



Jan. 23, 1945. M. c. GODDARD TELEPHONE SYSTEM Filed March 23, 1940 3'Sheets-Sheet l INVENTOR MCZGODDARD Y MWW M ATTORNE V Jan. 23, 1 945.

Filed March 23, 1940 3 Sheets-Sheet 2 H F Nb P v V N W W" 4 E Q R W R L m A h [m 1 i UH 9% To a NR \(i .0 v 4% R H r U nu 4 \IMI INVENTOR M C. GODDARD w WT W 4W ATTORNE V Jan. 23, 1945. Q GODDARD 2,367,769

TELEPHONE SYSTEM Filed.March 23, 1940 3 Sheets-Sheet 3 N [/5 N TOR By MC. GODDARD WWW A TTOPA/FV Patented Jan. 23, 1945 TELEPHONE SYSTEM Myron C. Goddard, Garden City, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March 23, 1940, Serial No. 325,511

Claims.

This invention relates to telephone systems and particularly to systems comprising subscriber controlled switching mechanism for completing desired connections.

Objects of the invention are an increase in the efficiency and flexibility of automatic .telephone systems.

A feature of the invention is a telephone system comprising a trunk circuit common to both coin and non-coin subscribers stations and arranged to make a test when taken for use to determine whether or not the call is from a coin station and, if so, to prevent completion of a talking connection when the called subscriber answers until the calling subscriber has deposited a coin. To enable determination of the character of the calling station, either the noncoin subscribers stations or the coin subscribers stations are arranged to connect ground potential through a high impedance to the line conductors upon removal of the receiver to initiate a call.

A second feature of the invention is a telephone system comprising coin and non-coin, subscribers stations in which both coin and noncoin stations are connected to a single line and in which means comprising a trunk circuit is provided for identifying the character of the calling station and for preventing the completion of a talking connection when the called subscriber answers, if the call originated at the coin station, until the calling subscriber has deposited a coin.

Another feature of the invention is a telephone system comprising coin lines, non-coin lines, and lines each of which is connected to a coin station and also to a non-coin station, and including a trunk circuit common to all of said lines and arranged to make a test when connected to any line having a coin station thereon for determining Whether the calling station is a coin station and, if so, to prevent closure of a talking connection when the called subscriber answers until the calling subscriber deposits a coin.

Another feature of the invention is means inphone system in which the invention is embodied, one such system being represented schematically in the drawing which forms a part of this specification. The invention is not limited in its application to the particular system shown but is generally'applicable to automatic telephone systems comprising coin and non-coin subscribers stations.

Referring to the drawings:

Fig. 1 shows subscribers lines Ll, L2, L3- and L4, flat-rate subscribers stations A, D and E, coin subscribers stations B and C, a line-finder switch LFI, a connectorswitch C2, and a trunk circuit C'I-l; and

2nd edition of Automatic Telephony by Smith,

and Campbell for a complete description of the structure of such switches and their operation when used as selectors and connectors. Reference may be had to the patent to R. L. Stokely No. 1,799,654 granted April 7, 1931, for a description of the operation of such a switch when used as a line finder. The line-finder switch LFI is represented in the drawings by a set of brushes 25, 26 and 21, four sets of terminals 2|, 22, 23 and 24 and three sets of shaft-operated contact springs 28, 29 and 30. The magnets, relays and other apparatus associated with switches LF-l are not shown in the drawings. The selector Sl is shown as having direct access to connector switches C--l but it is of course understood that. intermediate selectors may be provided if the numbering system so requires. The connector C-l is represented in the drawings by brushes 9!, 92 and 93, one set of terminals, relays 8|, 82 and 84 and talking condensers and the connector C2 is represented in the drawings by a set of brushes and two sets of terminals, none of the associated relays, magnets and other apparatus being shown.

The subscribers station. A is a local-service, flat-rate'station comprising a transmitter 3, receiver 4, dial 5, a ringer 6 normally connected through condenser 1 to the lower conductor of lineLl, and an induction coil 8. Upon removal ofreceiver 4, from the hook, both conductors of line L| are connected through the ringer 6, to ground. The subscribers station E is a local service post-payment coin-box station comprisin a transmitter I3, receiver |4, dial IS, a ringer l6 normally connected through condenser H to the upper conductor of line L| an induction coil l8, a resistor l9, and coin contacts 20. The line LI is connected to two sets of terminals in the banks of connector switches -2, the line conductors and 2 being transposed in their connection to these two sets of terminals so that the source of ringing current (not shown in the drawings) will be connected to the conductor 2 to actuate the ringer B when station A is called and to conductor to actuate the ringer |6 when station B is called. The station A is arranged so that upon removal of the receiver to originate a call, ground potential is connected through ringer 6 and contacts of the receiver-hook switch to both conductors of the line L| to indicate that the calling station is a non-coin station. The station B is arranged so that upon removal of the receiver to originate a call, there is no connection of ground potential to the conductors and 2. Station B includes coin-operated contacts 20 and a resistor I9 normally short-circuited by these contacts. The station C is a local-service, coin station similar to station B; the station D is a localservice, fiat-rate station; and the station E is an extended-service, fiat-rate station.

T e te mi s to which the line LI is connected, represent a level of the line-finder bank in which the lines are either coin or non-coin local-service lines, or lines serving both coin and non-coin, local-service stations; the terminals 22, to which the line L2 is connected, represent a level in which the lines are all local-service, coin lines; the terminals 23, to which the line L3 is connected, represent a level to which the lines are all local-service, flat-rate lines; and the terminals 24, to which the line L4 is connected. represent a level in which the lines are all extended-service, fiat-rate lines, that is, the lines of subscribers having free access to certain subscribers outside of the local area. The contact sprin s 28 are actuated when the brushes 25, 2B and 21 are on a level containing both coin and non-coin lines or lines serving both coin and noncoin stations; the contact springs 29 are actuated when the brushes are on a level containing coin lines only; the contact springs 30 are actuated when the brushes are on a level containing localservice, fiat-rate lines only; and none of the contact springs 28, 29 and 30 are actuated when the brushes are on a level containing extendedservice, fiat-rate lines only.

The coin trunk CT| comprises a polarized test relay 32 for testing a calling line if it is in a group in which there are both coin and non-coin lines or lines having both coin and non-coin stations connected thereto. Relay 33 is auxiliary to relay 32, and relays 35 and 31 control the connection of test relay 32 to the calling line. Relay 4| is a polarized supervisory relay which operates when the called subscriber answers to initiate a coin test on a call from a coin station to determine whether the calling subscriber has or has not deposited a coin. Relays 4|, 42, 43, 44, 45 and 48 function to make the test and to hold the talking circuit between the calling and called stations open until the coin has been deposited.

Since there are three classes of calling subscribers, it is necessary that means be provided for indicating, on calls to an operator, the class of the calling station. The trunk circuit TC3 and TC-4 are similar to the trunk circuits of the same designation disclosed in the patent to R. B. Buchanan et al., No. 2,233,282 issued Feb. 25, 1941. These trunk circuits are arranged to give the operator a tone signal of one character on calls from one class, a tone signal of a different character on calls from a second class, and to give the operator no tone signal on calls from lines of the third class. In order that the trunk circuit will know the character of the calling station, a control conductor 54 is provided between the line finder LF| and a brush 14 of selector S| through which an identifying signal may be transmitted to the trunk circuit TC3. If the calling station is a coin station, contact springs 28 or 29 are actuated to connect ground directly to conductor 54; if the calling station is a local-service, flat-rate station, contact springs 30 are actuated; or if a station test has been made, relay 33 has been actuated (as hereinafter described) to connect ground through a resistance 34 to conductor 54; and if the calling station is an extended-service, fiat-rate station none of springs 28, 29 or 30 are actuated, and relay 33 is not operated, and there is no connection of ground potential to conductor 54.

Assume now that a call is originated at the local-service, flat-rate station A, and that the line finder LF-| is thereupon actuated in the usual manner to connect with the set of terminals 2| and thereby close a circuit for operating the line relay 6| of the associated selector S-|. The circuit for operating relay 6| is traced from battery through the lower winding of this relay, a back contact of relay 64, conductor 52, lower winding of relay 4|, back contacts of relays 44, 31 and 35, brush 26 of line finder LF-I, conductor 2 of line Ll, left winding of induction coil 8, transmitter 3, normally closed contacts of dial 5, through the middle front contact of the receiver-hook switch thence through the ringer 6 to ground and also through the upper front contact of the receiver-hookswitch, conductor I of line LI, brush 25 of line finder LF-|, back contacts of relays 35, 3'! and 44, upper winding of relay 4|, conductor 5|, a back contact of relay 64, upper winding of relay 6|, normally closed contact of the 11th rotary step springs 11 and through the left winding of dial tone source 6|! to ground. Relay 6| is operatively energized and closes a circuit for operating relay 62. Relay 62 connects ground potential to conductor 53 to hold the line finder LF-| in usual manner. The polarized relay 4| does not operate in series with the line relay 6| since the current through its windings is not in the operating direction.

When the calling subscriber dials the first digit of the number of the subscriber with whom connection is desired, relay 6| is alternately released and reoperated in response to each impulse of the train created by the dialing operation. The first release of relay 6! closes a circuit for operating relay G3 and vertical stepping magnet 61. The operation of magnet 61 steps the brushes up to the first level of the bank. The vertical oiT- normal springs 10 are actuated when the shaft and brushes move out of normal position thereby closing a circuit which includes front contacts of relays 63 and 62 for operating relay 65. The release of relay 6| at the end of the first impulse causes the release of magnet 61 but relay 63 is slow in releasing and for this reason remains operated until after relay 6| has reoperated at the end of the last impulse in the train. Relay 62 is also slow to release and for this reason does not release while relay- 6l' is responding to dial. impulses. Relay 6'5: closesa locking circuitwhich includesthe back contact. of rotary steppingmagnet 68, the outer front contact. of relay 65 and a back contact of relay: B4. The release. and are-- operation of relay iii in response to each succeed-- i-ng impulse of the train created by the. dialing oithe first digit effects a reoperation and release. of magnet B l, thereby stepping the brushes up to they level corresponding to the digit dialed. When: relay 63 releases, after all of the impulses in the train have been received, a. circuit is closed for operating the rotary stepping magnet 63 thus advancing the brushes into engagement with the first set of terminals in the selected level. The operation of' magnet 68 causes the release of re-- lay 65 and the release of relay 65 causes the release of magnet 68. If the trunk, selector or connector circuit connected to the engaged set of terminals ishusy, the test terminal is marked by a lousy, ground potential which effects the reoperation of relay 65.. The circuit for; reoperatr ing relay 55 is traced from battery through the winding of this relay; upper contact of the VON springs EB, back contact of magnet 68, lower back contact of relay 64, and; through test brush 13. The reoperation oil relay 65 effects the reoperation of magnet 68 thus advancing the, brushes to the next, set of terminals in the level. The ad vance of the brushes. is, inthis; manner, continued until an idle set of terminals is encountered; or, if all of the trunks in the selected level are. busy the brushes are advanced by an eleventh rotary step to an overflow position in which springs 11 are actuated to disconnect the dial, tone source 58 and connect the a1l-trunks-b usy tone source it to the calling line. If and when an idle set of terminals is encountered, the terminal engaged by test brush I3 is not. marked by ground potential and relay 65 does not reoperate;v but relay 6 3 is operated in series with the winding of relay 65 to extend the connection from, conductor 52, 53 and 54 to and through brushes H, 1.2,;13 and M to the trunk or other circuit connected to the engaged terminals. Relay 54 disconnects relay 6| from conductors 5i and 52 thereby causing. the release, of relays iii and 52. Since relay $2 is slow in releasing, it maintains the connection of ground to conductor 53 until the circuit connected to the selected set of terminals effects the connectionof. holding ground potential to the terminal engaged by brush 13. Assuming. that the terminals of the selected level are connected directly to connector witches and, that. the seized terminals 15 ar connected. to the connector circuit C-i, the operation of relay 64 connects. conductors 5i and 52 to the windings of line relay 8!, thereby operating relay 8!. Relay 8!. closes a circuit for operating relay 82; and relay 82 connects ground otential to the terminal engaged by test brush T3 to hold relay 64 of selector S-l and to hold the line finder LF-l after relay 62 of selector S.-I releases.

When relay 63 operated, upon release of relay 8.] in response to the first dial impulse as above described, ground at the lower irontcontact of relay 62 was connected through the front contacts of. relay 63 to conductor 55 thereby operating relay 3'! of the coin trunk circuit CT--i, and since the call originated in a line group having both coin and non-coin stations, the operation of relay 31 initiates a test to determine the character of the calling'station. The spring 28 having been actuated when the brushes of the line finder LF-I were raised to-thelevel including the terminals. 2|. oi Imelda relay 3]; closes a. circuit: for operatingrelay' 35. The. circuitfor operating relay 35 includes afrcntcontact of relay 31, a front contact of springs .28., conductor 53 and the lower front. contact. ofrelay-6.2: of selector .S-l. With springs. 28 actuated, the upper biasing winding of polarized relay 3.2 is. energized to prepare this relay .for testing; the calling: line; and when relay 31: operates, the lower winding of relay 32 is energized, operatin relay 32. While relay 3! is operated, the. connections between the line Li and conductors SJ and 5.2 include the outer front contacts of: relay 31, which contacts close before the adjacent back contacts are opened so that the connection between the line LI and selector S is-continuously maintained. When relay 63 of selector S-l releases at the end of the dialing of thefirst digit, relay 3] releases, opening the operating circuit of relay 35. Since relay 35 is slow in releasing, the conductors of the calling line are momentarily connected through front contacts of relay 35 and back contacts of relay 3?. to the lower winding of test: relay 32. The call having originatcd at station A, relay 32 is held operated over line. conductor I and 2, to ground through the ringer 6'. While this test is in progress, i conductor 52 is connected through resistor 36, the i-nnerlower back contact of relay 3'! and the inner lower front: contact. of relay 35 to conductor 53 to operatively energize the lower winding of line relay 6 of'selector S--|- or the lower winding of the line relay 8 of the connector C! if the connection has been extended by selector S--!. When relay-35 releases, it closes a locking circuit through the lower winding of relay 32 in series with. the winding of auxiliary relay 33 before it opens the connection between the lower winding of relay 3:2 and the conductors of the calling line. Thus, on the call being described, relay 32 remains: energized and relay 33 operates when relay ill). releases. The operation of relay 33 connects ground through a resistor 34' to conductor 54 as an indication that the call is from a local-service, flat-rate station.

The calling subscriber dials the remaining digits ofthe called subscribers number, the last two digits being effective to control the operation of the connector switch Cl. The brushes 9|, 92 and 93 are thus advanced into engagement with terminals ofthe called line L5. If the line is idle, the called station E is signaled by connecting a ringing current source (not shown) to the line in usual manner. When the call is answered, the supervisory relay 84 of connector C-l is operated to interchange the connections between the conductors incoming to connector C-l and the wind ings of relay 8|, thereby reversing the current through conductors 5| and 52. The polarized relay M is operated by the reversed current but is without efiect on the call being described because of the aforementioned operation of relay 32. The talking connection between the calling and called stations includes condensers of connector CI. When the calling subscriber replaces the receiver on the receiver hook, relay 8| releases. The release-of relay causes the release of relay 82 and the release of relay 82 disconnects the holding ground potential from the terminal engaged by brush 13, thereby efiecting the release of relay 64 of selector S-| and the release of the holding relay (not shown) of the line finder LF-i. When the called subscriber also replaces the receiver,

relay 841 releases and the connector Cl is restored to normal in usual manner. The release of relay 6 K closes a circuit for operating the release magnet 63 thus restoring the elector S-I to normal. The circuit of magnet 69 is opened at springs 10 when the shaft reaches normal.

Assume next that a call is initiated at station E, that the call is extended, as above described, by line finder LFI and selector S-I When the lower winding of relay 32 is connected to the calling line, as above described, relay 32 releases because there i no identifying ground connection at the coin station B. Since relay 32 releases, relay 33 is not operated and conductor 54 is connected through the back contact of relay 33 and the middle contact of springs 28 directly to ground. When relay 35 releases, the calling line is reconnected to conductors 5| and 52 and the dialing of the remaining digits completes the connection through a connector CI to a called line L5. When the call is answered and relay 4| operates due to the reversal of the current through its windings, a circuit is closed for operating relay 46. This circuit is traced from battery at the back contact of relay 45, through the front contact of relay 4|, lowermost back contact of relay 44, winding of relay 45, back contact of relay 32, through a front contact of springs 28 to ground on conductor 53. Relay 45 operates and closes circuits for operating relays 42 and 43. Relay 42 closes a circuit from battery through the back contact of relay 45, and front contact of relay 4|, for operating relay 44. Relay 44 looks under control of relays 4| and 45, but independent of relay 42. Relay 44 opens the talking connection between the calling and called stations and closes a circuit from battery through the Winding of relay 43, front contact of relay 44, back contacts of relays 31 and 35, brush 25, conductor I, receiver hook contacts and coin contacts 20 at station B, contacts of dial I5, transmitter I3, left winding of induction coil I8, conductor 2, brush 26, back contacts of relays 35 and 31, front contact of relay 44, winding of relay 46, back contact of relay 32, front contact of springs 28, to ground on conductor 53. Relays 43 and 46 are held operated by the current in this circuit and tone source 39 is connected through condenser 38 and a front contact of relay 44 in parallel with relay 46 thereby transmitting a tone signal to the calling station to indicate that the called subscriber has answered and that a coin should, be deposited. Relay 42 also closes a circuit including resistor 50 and a back contact of relay 4'! for holding relays 4| and 8| operated. When a coin is deposited, the contacts 20 are momentarily opened, thereby inserting the high resistance of resistor I9 in series with relays 43 and 46. Relay 48 remains operated but relay 43 is marginal and releases, closing a circuit for operating relay 45. Relay 45 looks and opens the circuit for holding relay 44. The release of relay 44 opens the test circuit through relays 43 and 46 and closes the talking connection between the calling and called stations. The release of relay 46 causes the release of relay 42 and prevents the reoperation of relay 43. The release of relay 42 opens the holding circuit through resistor 50 for relay 4| and 8|; and relays 4| and 8| are now held under control of the calling station. Release is effected, as above described, on a call from station IA, the disconnection of ground from conductor 53 being effective to release relay 45.

In order to discourage an attempt on the part of the calling subscriber, by manipulation of the dial or otherwise, to complete the talking connection without deposit of a coin, the circuit is arranged so that release of relay 46 causes the release of relay 42; and the release of relay 42, while relay 43 is released, closes a circuit for operating relay 41. Relay 41 locks, holds relay 44 operated and opens the hOldil'lg circuit through resistor 50 so that relays 4| and 8| release. The selector S-I and line finder LFI are thereupon restored to normal and the calling subscriber becomes connected to another selector S-I as if originating a new call. When ground is disconnected from conductor 53, relay 4'! releases and so also do relays 42, 43 and 46, if then operated. The release of relays 4| and 41 causes the release of relay.44.

If, on a call originating at station A of line LI, or at any other local-service, flat rate station on a line in a group of lines serving both coin and non-coin stations, the selector S-I is directively operated to select a level in which the terminals are connected to trunks to an operator's position,

the station identification test is made when relay 53 releases at the end of the first train of dial impulses, as hereinbefore described. The selector is automatically operated to hunt in the selected level and seize a set of terminals I6, connected to an idle outgoing trunk circuit TC3. The operation of relay 64 connects the calling line to the trunk circuit TC3, operating line relay I86. Relay I68 closes circuits for operating relays I84 and I90. Rela I84 connects ground, through conductor I91, to the terminal engaged by brush 73 to hold relay 64 operated. This ground potential is further extended through a front contact of relay 54 to conductor 53 to hold the line finder LF-l in usual manner. Relay I closes a circuit for operating the motor start relay MS of the common tone and ringing interrupter. Relay I33 interchanges the normally closed connections between the windings of relay I89 and the right windings of repeating coil RC3 to reverse the current through the conductors of the trunk so as to operate the polarized relay I00 of trunk circuit TC4. Relay I00 closes a circuit for operating relay Hit; and relay I0| closes a circuit for light ing the answering lamp I I3, to signal an operator. The ringing tone source I92 is connected through condenser I9I, inner lower contact of relay I84, and a back contact of relay I80, to conductor I96 to transmit a ringing tone to the calling line to indicate that an operator is being signaled. The shaft-operated springs 28 being operated, the station identification test having been made, and relay 33 having been operated, as above described on the call from station A to station E, ground potential is connected through resistor 34, front contact of relay 33, conductor 54, middle lower front contact of relay 64, and through brush I4 to conductor I98 of trunk circuit TC-3 to partially operate relay I83, to close a circuit for operating the slow-to-release relay I02. When the call is answered by inserting the plug of a cord in jack I I2, battery (not'shown) is connected through the sleeve conductor of the cord and jack to the windings of relay I 05. Relay I05 operates, closing a circuit for operating relay I06. Relay I 06 short-circuits the high resistance, upper winding of relay I00, thereby increasing the current through the conductors of the trunk to operate the marginal relay I89 of trunk circuit TC3. The operation of relay I06 causes the release of relay IOI to extinguish lamp H3 and closes a circuit for operating relay I01 to close the talking connection between repeating coil RC4 and the answering operatcrs telephone. The operation of relay I39 closes a circuit for operating relay 64 and to hold the line finder LF.|.

Hill. Relay 180 closesa circuit for holding relay I84 so as to place the connection under the joint control of the calling subscriber and answering operator, opens the ringing tone circuit through condenser |9| and causes the release of relay 182. While relay 82 .is releasing, the right winding of tone source |94 is connected through the back contact of relay I83, condenser H39, and front contacts of relays I82 and I86 to conductor I 36, thereby momentarily transmitting a distinctive tone to the answering operator to indicate that the calling station is a local-service, fiatrate station. The trunk circuit TC-B does not reverse the current through conductors 5| and 52 when the operator answers and, for this reason, relay M is not operated.

If, on a call originating at station B of line Lil, or at any other coin station on a line in a group of lines serving both coin and non-coin stations, the selector S| is directively operated to select a level in which the terminals are connected to an operator, the stationidentification test is. made as hereinoefore described, and the selector is automatically operated to seize a set of terminals l6 connected to an idle .outgoing trunk circuit TC-3. The operation of relay 64 connects the calling line to the trunk circuit TC--3, which thereupon effects the operation of the calling signal at .the operators position and connects ground potential to the terminal engaged by brush 13 to hold relay The shaftoperated springs 28 being operated and the station identification test having been ineffective to operate relay 33, ground potential is connected from conductor 53, through the middle contact of springs 28, back contact of relay 33, conductor 5t, front contact of relay 64, and through brush to conductor I98 tocompletely operate relay i855. When the call is answered, relay |=8il is operated, as above described. While relay W2 is releasing, the right winding of tone source I83 is connected through a front contact of relay H33, condenser 593, front contacts of relays Hi2 and MB, to conductor I96, thereby momentarily transmitting a different distinctive tone to the answer ing operator to indicate that the calling station is a coin station. Since the trunk circuit TC-3 doesno-t reverse the current through conductors 5i and 52 when the operator answers, relay -4| does not operate and the talking connection is completed without the deposit of a coin at the calling station.

Assume next that a call is initiated at a coin station such as C on a line in a group of lines serving coin stations only, in which case the springs 29 are actuated when. the brushes of the line finder LF| are on the level in which the terminals of the calling line are located. Upon connection of the calling line to the trunk circuit CT|, the selector 8-1 is directively operated to select a level corresponding to the first digit dialed by the calling subscriber. Since the springs 28 are not actuated, the operation of relay 3'! does not cause the operation of relay 35, and no station identification test is made when relay 31 releases. If the call is completed through a connector C| to a called subscribers line, the reversal of current when the call is answered effects the operation of relay 4| and, with ground connected through the right contact of springs 29 to the winding of relay 46, the trunk circuit CT| operates, as above described, on the call from station B to hold the talking .connection open until a .coinis depostied at the calling station. If, however, the call is a-call to the operator, seizure of the outgoing trunk circuit TIC-,3 effects the operation of the calling signal at the operators position. The trunk circuit TC-3 does not reverse the current through -.cond-uctors 5| and 52 when the operator answers, and relay 4| remains normalso that the talking connection is completed without the deposit of a coin at the calling station. .Due to the connection of ground potential from conductor 53 through the left contact of springs 29, back contact of relay 33 .to conductor 54 and thence through brush 74 to trunk circuit TC-3, this trunk circuit efiects the transmission of the coin-station'tone to the answering operator in themanner above described.

Assume next that a call isinitiated at a local- .service, flat-rate station such as D on a line in a group of lines serving subscribers stations all of the same class, in which case the springs 30 are actuated when the brushes of line finder LF| are on the level in which the terminals of the calling line are located. Upon connection of the callingline to trunk circuit CFI|,-the selectors-l is directively operated to select a level corresponding to the first digit dialed by the calling subscriber. Since springs 28 are not actuated, no station identification test is .made. If thecallis completed through a connector C-| to a called subscribers line, the operation of relay 4| due to the reversal of current when the call is answered does not cause the opening of the talking connection as on a call from a coin station because, without springs 28 .or 29 actuated, there is no connection of ground potential to the winding of relay 46. If the call is a call to the operator, seizure of an outgoing trunk circuit TC-3 effects the operation of the calling signal at the operators position. Ground potential is connected from conductor 53, through the contact closed by the actuationof springs 30, resistor 3|, back contact of relay 33, conductor 54 and brush 14 to the trunkv circuit TC3 to momentarily effect the transmission of the local-service, fiatrate tone to the answering operator. Since the trunk circuit does notreverse the current through conductors 5| and .52 when the operator answers, relay 4| does not operate.

Assume now that a. call is .initiated at an extended-service, fiat-rate station such as E on a line in a group serving subscribers stations all of the same class, in which case none of the springs 28, 29and 30 are actuated when the brushes of line finder LF| are on the level in which the terminals ofthe calling line are located. Upon connection of the calling line to trunk circuit CT-I the selector S-| is directively operated to select a level corresponding to the first digit dialed by the calling subscriber. .Since springs 28 are not actuated, no station identification test is made. If the call is completed through a connector C| .to a called subscriber s line, the operation of relay dueto the reversal of current when the call is answered does not cause the opening of the talking connection as on a call from a coin station because, without springs .28 or 29 actuated, there is no connection of ground potential .to the winding of relay 46. If the call is a call to the operator, seizure of an outgoing trunk circuit TC--3 efiects the operation of the calling signal at the operatorsposition. Since none of springs .28 29 and 30 areactuated, there is no connection of ground potential either directly or through a resistance to conductor 54 and relays I83 and I82 of the trunk circuitTC-3 are not operated. Therefore, no class ofservice tone transmitted to the answering operator, the lack of tone being indicative of the fact that the call originated at an extended-service, flat-rate station.

What is claimed is:

i. In a telephone system, subscribers lines, a group of said lines including both coin and noncoin lines, means including a trunk circuit for establishing a talking connection between any line in said group when calling and a called line, means for connecting any calling line in said group to said trunk circuit, means including testing means in said trunk circuit for determining whether a connected calling line is a coin line or a non-coin line, and means in said trunk circuit effective only if the calling line is a coin line for holding open the talking connection between the calling and called lines until a coin has been deposited by the calling subscriber.

2. In a telephone system, lines, subscribers stations connected to said lines, some of said stations being coin stations and others being noncoin stations, a trunk circuit common to said lines, means for connecting a calling line to said trunk circuit, means including testing means in said trunk circuit for determining whether the calling station is a coin station or a non-coin station, subscriber controlled means for completing a connection from the calling line connected to said trunk circuit to a called line, and means in said trunk circuit for holding the talking connection between a calling coin station and the called line open until a coin is deposited by the calling subscriber.

3. In a telephone system, subscribers lines, coin stations, non-coin stations, mean at said stations distinguishing the coin stations from the non-coin stations, a trunk circuit common to lines serving both coin and non-coin stations, means for connecting a calling line to said trunk circuit, means in said trunk circuit for testing a connected calling line to determine whether the calling station is a coin station or a non-coin station, subscriber controlled means for completing a talking connection from the calling line connected to said trunk circuit to a called line, and means in said trunk circuit efiective only in case the call is from a coin station for holding the talking connection open until a coin is deposited by the calling subscriber.

4. In a telephone system, subscribers lines including a line having a non-coin station and a coin station connected thereto, a trunk circuit, means for connecting said lines to said trunk circuit upon the initiation of a call at either of said stations, and means including testing means in said trunk circuit for determining whether the calling station is a coin station or a non-coin station, subscriber controlled means for completing a connection from the calling line to a called line, and means in said trunk circuit effective only if the calling station is a coin station for holding the talking connection between the calling and called lines open until a coin is deposited at the calling station.

5. In a telephone system, subscribers lines, means comprising a selector for establishing a connection between a calling line and a called line, a party line having both a fiat-rate station and a coin-box station connected thereto, means effective upon the origination of a call at either one of said stations for connecting said party line to said selector,,a trunk circuit included in the connection between said line and said selector, means at said stations efiective upon origination of a call to indicate whether the call is from the flat-rate or from the coin-box station, testing means in said trunk circuit for determining which of said stations is the calling station, and means in said trunk circuit efiective only if the call is from a coin-box station for opening the talking connection between the calling and called lines in response to the answer of the called subscriber and for again closing the talking connection in response to the deposit of a coin at the calling station.

6. In a telephone system, subscribers lines, a group of lines including lines serving coin stations only, lines serving non-coin stations only, and a line serving both a coin and a non-coin station, a trunk circuit, means for connecting any of the lines in said group to said trunk circuit, means including testing means in said trunk circuit for determining whether a connected calling station is a coin station or a non-coin station, subscriber controlled means for completing a connection with a called line, and means in said trunk circuit for holding the talking connection between the calling and the called lines open until a coin is deposited at the calling station.

7. In a telephone system, subscribers lines including a line serving a coin station and a noncoin station, a trunk circuit, means for connecting said line to said trunk circuit responsive to the initiation of a call at either of said stations, means, including means in said trunk circuit for testing said line, for determining whether the calling station is a coin station or. a non-coin station, an operators position, trunks terminating at said position, subscriber controlled means for completing a connection from the calling line to a called line or to one of said trunks, an outgoing trunk circuit associated with each of said trunks and arranged to transmit a calling signal to the operators position responsive to the connection of a calling line thereto and arranged to transmit either one of two tones to the operator, means including means in the first-mentioned trunk circuit for transmitting a signal to a connected outgoing trunk circuit indicative of the character of the calling station, and means in said outgoing trunk circuit responsive to said signal for transmitting to the answering operator the particular one of said tones which corresponds to the character of the calling station.

8. In a telephone system, subscribers lines including a line serving a coin station and a noncoin station, a trunk circuit, means for connecting said line to said trunk circuit responsive to the initiation of a call at either of said stations, means, including means in said trunk circuit for testing said line for determining whether the calling station is a coin station or a non-coin station, an operators position, trunks terminating at said position, subscriber controlled means for completing a connection from the calling line to a called line or to one of said trunks, an outgoing trunk circuit associated with each of said trunks and arranged to transmit a calling signal to the operators position responsive to the connection or" a calling line thereto and arranged to transmit either one of two tones to the operator, means in the first-mentioned trunk circuit effective only on a call from said coin station to another subscribers line for holding the calling connection between the calling and called lines open until a coin is deposited at the calling station, means including means in the first-mentioned trunk circuit for-transmitting a signal to a connected outgoing trunk circuit, said signal indicative of the character of the calling station, and means in said outgoing trunk circuit responsive to said signal for transmitting to the answering operator the particular one of said tones which corresponds to the character of the calling station.

9. In a telephone system, subscribers lines, subscribers stations connected to said lines, said stations including local-service fiat-rate stations, extended-service fiat-rate stations, and coin sta tions, one of said lines serving a coin station and a non-coin station, a trunk circuit, means for connecting a calling line to said trunk circuit, means, including means in said trunk circuit for testing a calling line, for determining whether the calling station is a coin station or a non-coin station, an operators position, trunks terminating at said position, subscriber controlled means for completing a connection from the calling line to a called line or to one Of said trunks, an outgoing trunk circuit associated with each of said trunks and arranged to transmit a calling signal to said position responsive to connection of a calling line thereto, means including means in the first-mentioned trunk circuit for indicating to a connected outgoing trunk circuit the character of the calling station, and means in said outgoing trunk circuit for indicating to the answering operator the character of the calling station.

10. In a telephone system, subscribers lines,

subscribers stations connected to said lines, said stations including local-service flat-rate stations, extended-service fiat-rate stations, and coin stations, one of said lines serving a coin station and a non-coin station, a trunk circuit, means for connecting a calling line to said trunk circuit, means, including means in said trunk circuit for testing a calling line, for determining whether the calling station is a coin station or a noncoin station, an operators position, trunks terminating at said position, subscriber controlled means for completing a connection from the calling line to a called line or to one of said trunks, an outgoing trunk circuit associated with each of said trunks and arranged to transmit a calling signal to said position responsive to connection of a calling line thereto, means in the first-mentioned trunk circuit effective only on a call from a coin station to another subscribers line for holding the talking connection between the calling and called lines open until a coin is deposited at the calling station, means including means in the first-mentioned trunk circuit for indicating to a connected outgoing trunk circuit the character of the calling station, and means in said outgoing trunk circuit for indicating to the answering operator the character of the calling station.

MYRON C. GODDARD. 

